package com.example.offer;

/**
 * 189. 轮转数组
 * 给你一个数组，将数组中的元素向右轮转 k 个位置，其中 k 是非负数。
 * <p>
 * <p>
 * <p>
 * 示例 1:
 * <p>
 * 输入: nums = [1,2,3,4,5,6,7], k = 3
 * 输出: [5,6,7,1,2,3,4]
 * 解释:
 * 向右轮转 1 步: [7,1,2,3,4,5,6]
 * 向右轮转 2 步: [6,7,1,2,3,4,5]
 * 向右轮转 3 步: [5,6,7,1,2,3,4]
 * 示例 2:
 * <p>
 * 输入：nums = [-1,-100,3,99], k = 2
 * 输出：[3,99,-1,-100]
 * 解释:
 * 向右轮转 1 步: [99,-1,-100,3]
 * 向右轮转 2 步: [3,99,-1,-100]
 * <p>
 * 思路：
 * nums = "----->-->"; k =3
 * result = "-->----->";
 * <p>
 * reverse "----->-->" we can get "<--<-----"
 * reverse "<--" we can get "--><-----"
 * reverse "<-----" we can get "-->----->"
 * this visualization help me figure it out :)
 */
public class Rotate {
    public void rotate(int[] nums, int k) {
        int n = nums.length;
        if (n <= 1) return;
        k %= n;
        reverse(nums, 0, n - 1);
        reverse(nums, 0, k - 1);
        reverse(nums, k, n - 1);
    }

    void reverse(int[] nums, int start, int end) {
        while (start < end) {
            int temp = nums[start];
            nums[start] = nums[end];
            nums[end] = temp;
            end--;
            start++;
        }
    }
}
